Pixel Structure of Flat Panel Detection Device, Flat Panel Detection Device and Camera System

ABSTRACT

A pixel structure of flat panel detection device, a flat panel detection device, and a camera system. The pixel structure of the flat panel detection device includes a photodiode configured to collect optical signals and convert the optical signals into electrical signals, the photodiode includes a positive terminal and a negative terminal, the negative terminal is connected to a bias voltage signal terminal; a signal amplification circuit, a signal input terminal of the signal amplification circuit is connected to the negative terminal of the photodiode, a signal output terminal of the signal amplification circuit is connected to a first node; a first switching transistor, a control electrode of the first switching transistor is connected to a scanning signal line, a first terminal of the first switching transistor is connected to a data signal line, and a second terminal of the first switching transistor is connected to the first node.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority of the Chinese PatentApplication No. 201910009421.3, entitled “Pixel Structure of Flat PanelDetection Device, Flat Panel Detection Device, and Camera System” andfiled on Jan. 4, 2019 with CNIPA, the disclosure of which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

Embodiments of the present disclosure relate to a pixel structure of aflat panel detection device, a flat panel detection device, and a camerasystem.

BACKGROUND

Digital X-ray (Digital Radiography, DR) technology is widely used inmedical equipment, such as X-ray machines for emitting X-ray. The keycomponent of the DR device is a flat panel detection device forcollecting images, and its performance will greatly effect on thequality of the DR images.

SUMMARY

Embodiments of the present disclosure provide a pixel structure of aflat panel detection device, a flat panel detection device, and a camerasystem.

At least one embodiment of the present disclosure provides a pixelstructure of a flat panel detection device, comprising: a photodiodeconfigured to collect optical signals and convert the optical signalsinto electrical signals, the photodiode comprises a positive terminaland a negative terminal, and the negative terminal is connected to abias voltage signal terminal; a signal amplification circuit, a signalinput terminal of the signal amplification circuit is connected to thenegative terminal of the photodiode, and a signal output terminal of thesignal amplification circuit is connected to a first node; and a firstswitching transistor, a control electrode of the first switchingtransistor is connected to a scanning signal line, a first terminal ofthe first switching transistor is connected to a data signal line, and asecond terminal of the first switching transistor is connected to thefirst node.

For example, the signal amplification circuit comprises: a secondswitching transistor, a control electrode of the second switchingtransistor is connected to a first voltage signal terminal, a firstterminal of the second switching transistor is connected to a secondvoltage signal terminal, a second terminal of the second switchingtransistor is connected to a second node, and the second node and thefirst node are connected together to become one node; a third switchingtransistor, a control electrode of the third switching transistor isconnected to the second node, and a first terminal of the thirdswitching transistor is the signal input terminal of the signalamplification circuit; and a bootstrap circuit, one terminal of thebootstrap circuit is connected to the second terminal of the thirdswitching transistor, and the other terminal of the bootstrap circuit isthe signal output terminal of the signal amplification circuit.

For example, the bootstrap circuit is a capacitor.

For example, the photodiode is a metal-semiconductor-metal typephotodiode structure.

For example, the third switching transistor is an n-type thin filmtransistor.

For example, the photodiode is a PIN-type photodiode structure.

For example, the third switching transistor is a p-type thin filmtransistor.

For example, the pixel structure further comprises an X-ray conversionlayer disposed on the photodiode, and the X-ray conversion layer isconfigured to convert a X-ray into an optical signal.

For example, the pixel structure further comprises a signal readoutcircuit, and the signal readout circuit is connected to the data signalline.

For example, the X-ray conversion layer is made of gadolinium oxysulfideor cesium iodide material.

For example, the metal-semiconductor-metal type photodiode structurecomprises: a substrate; a gate electrode and a first ground layer formedon the substrate; a gate insulating layer formed on the gate electrodeand the first ground layer; a first active layer formed on the gateinsulating layer corresponding to the gate electrode; a source-drainlayer formed on the first active layer; a first intermediate insulationlayer formed on the source-drain layer; a first via hole formed in thefirst intermediate insulation layer; a second ground layer formed on thefirst intermediate insulation layer; a second intermediate insulationlayer formed on the second ground layer and the first intermediateinsulation layer; a second via hole formed in the second intermediateinsulation layer, and the second via hole is communicated with the firstvia hole; an electrode formed on the second intermediate insulationlayer; and a second active layer formed on the second intermediateinsulation layer and the electrode.

For example, the PIN-type photodiode structure comprises: a substrate; agate electrode formed on the substrate; a gate insulating layer formedon the gate electrode; an active layer formed on the gate insulatinglayer corresponding to a position of the gate electrode; a source-drainlayer formed on the active layer; a first passivation layer formed onthe source-drain layer; a second source-drain layer formed on the firstpassivation layer; a PIN junction formed on the second source-drainlayer; an ITO cover layer formed on the PIN junction; an intermediateinsulation layer formed on the ITO cover layer; a second passivationlayer formed on the intermediate insulation layer; a shielding layerformed on the second passivation layer; and a protective layer formed onthe shielding layer. The X-ray conversion layer is formed on theprotective layer.

At least one embodiment also provides a flat panel detection device,comprising the pixel structure of the flat panel detection device.

At least one embodiment also provides a camera system, comprising theflat panel detection device.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the present disclosure will be described in moredetail below with reference to the accompanying drawings, so that thoseskilled in the art can more clearly understand the embodiments of thepresent disclosure, in which

FIG. 1A is a circuit diagram of a pixel structure of a flat paneldetection device provided by an embodiment of the present disclosure;

FIG. 1B is a circuit diagram of a pixel structure of a flat paneldetection device provided by an embodiment of the present disclosure,where T3 is a p-type transistor;

FIG. 2A is a PIN photodiode structure with an X-ray conversion layerprovided by an embodiment of the present disclosure;

FIG. 2B is a schematic diagram of the structure of an MSM-typephotodiode provided by an embodiment of the present disclosure;

FIG. 3 is a circuit signal simulation diagram of a pixel structure of aflat panel detection device provided by an embodiment of the presentdisclosure;

FIG. 4 is a circuit signal simulation diagram of a pixel structure of aflat panel detection device provided by an embodiment of the presentdisclosure; and

FIG. 5 is a signal readout circuit diagram of an embodiment of thepresent disclosure.

DETAILED DESCRIPTION

The technical solutions of the embodiments will be described in aclearly and fully understandable way in connection with the drawingsrelated to the embodiments of the disclosure. Apparently, the describedembodiments are just a part but not all of the embodiments of thedisclosure. Based on the described embodiments herein, those skilled inthe art can obtain other embodiment(s), without any inventive work,which should be within the scope of the disclosure. It should be notedthat the same or similar reference numerals throughout indicate the sameor similar elements or elements having the same or similar functions.The embodiments described below with reference to the drawings areexemplary, which are provided only for the purpose of explaining thepresent disclosure, and should not be construed as limiting the presentdisclosure. It is to be noted that same or similar reference numeralsrepresent same or similar elements or elements with same or similarfunctions throughout the context. Embodiments described with referenceto the drawings are exemplary embodiments, which are used for explainingthe disclosure, and cannot be understood as a limitation to the presentdisclosure.

Unless otherwise defined, all the technical and scientific terms usedherein have the same meanings as commonly understood by one of ordinaryskill in the art to which the present disclosure belongs. The terms,such as “first,” “second,” or the like, which are used in thedescription and the claims of the present disclosure, are not intendedto indicate any sequence, amount or importance, but for distinguishingvarious components. The terms, such as “comprise/comprising,”“include/including,” or the like are intended to specify that theelements or the objects stated before these terms encompass the elementsor the objects and equivalents thereof listed after these terms, but notpreclude other elements or objects. The terms, “on,” “under,” etc. areonly used to indicate relative position relationship, and when theabsolute position of the object which is described is changed, therelative position relationship may be changed accordingly.

An important evaluation index of the performance of the flat paneldetection device is the signal-to-noise ratio (SNR), that is, the largerthe amount of signals is and the smaller the noise is, the better thedetection effect of the flat panel detection device is. However, in theprocess of collecting images, the bones and soft tissues of the humanbody absorb a large amount of X-rays. As a result, when this part of thesignals reaches the surface of the flat panel detection device, theamount of the signals is extremely low, so the effective amount ofsignals collected and converted is low. Although the terminal obtainsinformation about bones and soft tissues through the reverse processingof the image, the signals are greatly affected by noise due to the loweramount of signals collected previously, that is, this part of thesignals is easily contaminated, which reduces the detection effect ofthe flat panel detection device, and reduce the quality of the obtainedimage.

Embodiments of the present disclosure provide a pixel design method ofan X-ray detection device. In addition to other structures to bediscussed below, the use of two TFTs and one capacitor to increase thedetection ray signal is beneficial to improve the signal-to-noise ratio(SNR) of the flat panel detection device. For example, the solutions ofthe embodiments of the present disclosure are suitable for pixel designswith high fill rates, such as MSM-type FPXD (Flat Panel X-ray Detection)and full-layer PIN-type FPXD products, and the increased pixels do notdecrease the additional pixels fill rate.

The embodiments of the present disclosure provide a pixel structure of aflat panel detection device. The flat panel detection device can beapplied to a camera system of a medical device, such as a CCD (ChargeCoupled Device) camera system, CMOS (Complementary Metal OxideSemiconductor) camera system. The flat panel detection device may be anX-ray flat panel detection device, and the X-ray flat panel detectiondevice may be divided into two types, i.e., a direct conversion type oran indirect conversion type.

As illustrated in FIG. 1A, the pixel structure of the flat paneldetection device may include a photodiode PD, a signal amplificationcircuit, and a first switching transistor T1. The photodiode PD is usedto collect an optical signal and convert the optical signal into anelectrical signal, the photodiode PD has a positive terminal and anegative terminal, and the negative terminal is connected to a biasvoltage signal terminal Bias; a signal input terminal of the signalamplification circuit is connected to the negative terminal of thephotodiode PD, a signal output terminal of the signal amplificationcircuit is connected to a first node P1; a control electrode of thefirst switching transistor T1 is connected to a scanning signal lineGate, a first terminal of the first switching transistor T1 is connectedto a data signal line Data, and a second terminal of the first switchingtransistor T1 is connected to the first node P1.

In this embodiment, the photodiode PD has a unidirectional conductivity,and the photodiode PD works under the action of a reverse voltage. Thisphotodiode PD can convert collected optical signals into electricalsignals, that is, the photodiode PD will generate hole electron pairswhen exposed to light. Under the action of an external bias field, theelectron and hole pairs move in opposite directions to form current, andthe current forms stored charges in the storage capacitor of thephotodiode PD. When a scan signal written through the scan signal lineGate causes the first switching transistor T1 to be turned on, thephotodiode PD can output a given voltage signal to the signalamplification circuit and this voltage signal can be amplified by thesignal amplification circuit and then output to the data line Data. Inother words, in this process, the signal amplification circuit isprovided between the photodiode PD and the first switching transistor T1to increase the actual signal output to the data line Data, that is, thedetection signal of the flat panel detection device is increased, whichis beneficial to improve the signal-to-noise ratio of the flat paneldetection device, improve the detection effect of the flat paneldetection device and improve the quality of the obtained images.

For example, as shown in FIG. 1A, the signal amplification circuit 100(as shown in the shallow frame in FIG. 1A) may include a secondswitching transistor T2; a third switching transistor T3; and abootstrap circuit, such as a capacitor C. A control electrode of thesecond switching transistor T2 is connected to a first voltage signalterminal V1, a first terminal of the second switching transistor T2 isconnected to a second voltage signal terminal V2, and a second terminalof the second switching transistor T2 is connected to a second node P2.The second node P2 is connected to the first node P1, so the two nodescan be regarded as one node. A control electrode of the third switchingtransistor T3 is connected to the second node P2, and a first terminalof the third switching transistor T3 is the signal input terminal of thesignal amplification circuit; a second terminal of the third switchingtransistor T3 is connected to one terminal of the bootstrap circuit, andthe other terminal of the bootstrap circuit is the signal outputterminal of the signal amplification circuit.

The bootstrap circuit, also referred to a boost circuit, makes use ofelectronic components, such as a bootstrap boost diode or a bootstrapboost capacitor, to superimpose the capacitor discharge voltage and thepower supply voltage, so as to increase the voltage.

In this embodiment, the signal amplification circuit amplifies thevoltage signals output by the photodiode PD by using two switchingtransistors in combination with a bootstrap circuit. This design cansimplify the difficulty of making the signal amplification circuit andreduce the space occupied by the signal amplification circuit, which canalleviate the situation that this signal amplification circuit occupiesthe space of other pixels, and ensure the pixel fill rate of the flatpanel detection device.

Based on the above embodiment, the working principle of the pixelstructure of the flat panel detection device may be as follows: whenexposed to light, the photodiode PD collects optical signals andconverts the optical signals into electrical signals for storing theelectrical signals in its own capacitance; when a scan signal causes thefirst switching transistor T1 to be turned on, a first voltage isapplied to the control electrode of the second switching transistor T2through the first voltage signal terminal V1 to turn on the secondswitching transistor T2, so that a second voltage written through thesecond voltage signal terminal V2 is applied to the control electrode ofthe third switching transistor T3 to turn on the third switchingtransistor T3; when the third switching transistor T3 is turned on, thevoltage signal output by the photodiode PD can be input to the bootstrapcircuit through the third switching transistor T3, and output to thedata line Data through the first switching transistor T1 after beingboosted by the bootstrap circuit, which realize the amplification of thesignals.

For example, as illustrated in FIG. 1A, the aforementioned bootstrapcircuit may be a capacitor C, and the amplification of the signals maybe realized by using the characteristics that the voltage across thecapacitor C cannot be changed abruptly. In other words, when there is agiven voltage difference between the two terminals of the capacitor C,the voltage at the input terminal (this terminal is the terminal of thecapacitor C that is connected to the second terminal of the thirdswitching transistor T3) of the capacitor C is increased, the voltage atthe output terminal (this terminal is the signal output terminal of theaforementioned signal amplification circuit) of the capacitor C stillmaintains the original voltage difference relative to the inputterminal, which is equivalent to the voltage at the output terminal ofthe capacitor C being lifted by its input terminal, which realizes theamplification of the signals.

In this embodiment, the use of the capacitor C to amplify the signalscan further simplify the difficulty of making the signal amplificationcircuit and reduce the space occupied by the signal amplificationcircuit, which can alleviate the situation that this signalamplification circuit occupies the space of other pixels, which ensuresthe pixel fill rate of the flat panel detection device.

For example, the photodiode PD may be an MSM (Metal-Semiconductor-Metal)type photodiode. This MSM-type photodiode refers to a device in whichmetal electrodes are formed on the semiconductor surface to formmetal-semiconductor Schottky contacts. This MSM-type photodiode has aunique planar structure that makes the photodiode extremely easy forphotoelectric integration, and has the characteristics of high bandwidthand high speed. For example, this MSM-type photodiode can be made ofindium gallium arsenide (InGaAs) material. The MSM-type photodiode has awide response wavelength range, can work efficiently at roomtemperature, and has excellent characteristics, such as low darkcurrent, high response speed, and high sensitivity.

The voltage signal output by the MSM photodiode is usually a positivevoltage signal. Therefore, in order to amplify the positive voltagesignal output by the MSM-type photodiode to a greater positive voltage,the third switching transistor T3 may be an n-type thin film transistor.In addition, the first switching transistor T1 and the second switchingtransistor T2 may also be n-type thin film transistors.

In this embodiment, the negative terminal of the MSM photodiode can bewritten into a positive voltage through the bias voltage signal terminalbias. For example, the positive voltage may be about 200V, but theembodiment of the present disclosure is not limited thereto. When notexposed to light, the MSM-type photodiode is in the ‘off’ state, in thiscase, the first switching transistor T1, the second switching transistorT2, and the third switching transistor T3 can be turned on, and aninitial voltage value is written to the positive terminal of theMSM-type photodiode and the two terminals of the capacitor C through thedata line Data. This initial voltage value may be, for example, about1V, but the embodiment of the present disclosure is not limited thereto.When exposed to light, the MSM-type photodiode can convert the opticalsignals into electrical signals to make itself in a working state. Inthis case, the initial voltage value of the positive terminal of theMSM-type photodiode gradually approaches the voltage value at itsnegative terminal, that is, the voltage value at the positive terminalof the MSM-type photodiode (hereinafter referred to as the outputvoltage) becomes larger. When the scan signal written through the scansignal line Gate causes the first switching transistor T1 to be turnedon, the first voltage is applied to the control electrode of the secondswitching transistor T2 through the first voltage signal terminal V1 toturn on the second switching transistor T2, so that the second voltagewritten through the second voltage signal terminal V2 is applied to theoutput terminal of the capacitor C through the second node P2 and thefirst node P1 sequentially, which causes the two terminals of thecapacitor C have a given voltage difference, and the second voltage isapplied to the control electrode of the third switching transistor T3through the second node P2 to turn on the third switching transistor T3;when the third switching transistor T3 is turned on, the output voltageat the positive terminal of the MSM-type photodiode can be input to theinput terminal of the capacitor C through the third switching transistorT3, that is, the voltage at the input terminal of the capacitor Cbecomes larger; at this moment, the voltage of the output terminal ofthe capacitor C also increases in order to maintain the inherent voltagedifference of the capacitor C.

It is to be noted that, as mentioned above, in the case where thephotodiode PD is an MSM-type photodiode, both the second switchingtransistor T2 and the third switching transistor T3 may be n-type thinfilm transistors. In this way, to turn on the second switchingtransistor T2 and the third switching transistor T3, the voltageswritten by both the first voltage signal terminal V1 and the secondvoltage signal terminal V2 may both be positive voltages.

For example, in the case where the photodiode PD is an MSM-typephotodiode, a circuit signal simulation diagram of the pixel structuremay be as shown in FIG. 3. The abscissa in FIG. 3 represents the timing,and the unit is microseconds (vs); the longitudinal ordinate in FIG. 3represents voltages, and the unit is volts (V); the a in FIG. 3represents the change process of the voltage written by the firstvoltage signal terminal V1 over time, the b in FIG. 3 represents thechange process of the voltage written by the second voltage signalterminal V2 over time, the c in FIG. 3 represents the change process ofthe voltage output from the output terminal of the MSM-type photodiodeover time, and the d in FIG. 3 represents the change process of thevoltage output from the output terminal of the capacitor C over time.For example, as can be seen from FIG. 3, the voltage output by theMSM-type photodiode can be increased from a set voltage of about 8V toabout 22V by adjusting the timing of the signal, that is, the voltageoutput by the signal amplification circuit is about 22V at this moment,but the embodiment of the present disclosure is not limited thereto.

In another example embodiment, the photodiode PD may be a PIN-typephotodiode. This PIN-type photodiode has the advantages of smalljunction capacitance, short transit time, high sensitivity, etc., andlow noise. The voltage signal output by the PIN-type photodiode isusually a negative voltage signal (this negative voltage signal includes0V). In this way, to amplify the negative voltage signal output by thePIN photodiode to a smaller value (which refers to that the negativevalue of the voltage signal is smaller while the absolute value of thevoltage signal is greater), the third switching transistor T3 may be ap-type thin film transistor, and as shown in FIG. 1B, the firstswitching transistor T1 and the second switching transistor T2 may ben-type thin film transistors. For example, the third switchingtransistor may be a n-type thin film transistor. The configurations ofthe above-mentioned transistors may be same as a p-type or n-typetransistor in the related art.

In this embodiment, the negative terminal of the PIN-type photodiode canbe written into a negative voltage through the bias voltage signalterminal Bias. This negative voltage may be about −6V, but theembodiments of the present disclosure are not limited thereto. When notexposed to light, the PIN-type photodiode is in the ‘off’ state. In thiscase, the first switching transistor T1, the second switching transistorT2, and the third switching transistor T3 can be turned on, and aninitial voltage value can be written to the positive terminal of thePIN-type photodiode and the two terminals of the capacitor C through thedata line Data. This initial voltage value may be about 1V, but theembodiments of the present disclosure are not limited thereto. Whenexposed to light, the PIN-type photodiode can convert the opticalsignals into electrical signals to make itself in a working state. Inthis case, the initial voltage value of the positive terminal of thePIN-type photodiode gradually approaches the voltage at the negativeterminal of the photodiode, that is, the voltage value at the positiveterminal of the PIN type photodiode (hereinafter referred to as theoutput voltage) becomes smaller. As shown in FIG. 4, the output voltageof this PIN-type photodiode can become 0, but the embodiments of thepresent disclosure are not limited thereto, and the output voltage ofthis PIN-type photodiode may be smaller.

When the scan signal written through the scan signal line Gate causesthe first switching transistor T1 to be turned on, the first voltage (Asshown in FIG. 4, this first voltage may be about 8V, but the embodimentof the present disclosure is not limited to thereto) is applied to thegate electrode of the second switching transistor T2 through the firstvoltage signal terminal V1 to turn on the second switching transistorT2, so that the second voltage written through the second voltage signalterminal V2 is applied to the output terminal of the capacitor C throughthe second node P2 and the first node P1 sequentially, which causes thetwo terminals of the capacitor C have a given voltage difference, andthe second voltage (as shown in FIG. 4, the second voltage may be about−8V, but the embodiments of the present disclosure are not limitedthereto) is applied to the control electrode of the third switchingtransistor T3 through the second node P2 to turn on the third switchingtransistor T3; when the third switching transistor T3 is turned on, theoutput voltage at the positive terminal of the PIN-type photodiode canbe input to the input terminal of the capacitor C through the thirdswitching transistor T3, that is, the voltage at the input terminal ofthe capacitor C becomes smaller, for example, the voltage at the inputterminal of the capacitor C changes from about 1V to 0V; at this moment,the voltage of the output terminal of the capacitor C also decreases tomaintain the inherent voltage difference of the capacitor C.

For example, when the photodiode PD is a PIN-type photodiode, a circuitsignal simulation diagram of the pixel structure may be as shown in FIG.4, the abscissa in FIG. 4 represents the time/timing, and the unit ismicrosecond (vs); the longitudinal ordinate in FIG. 4 represents thevoltage, and the unit is volt (V); the a in FIG. 4 represents the changeprocess of the voltage written by the first voltage signal terminal V1over time, the b in FIG. 4 represents the change process of the voltagewritten by the second voltage signal terminal V2 over time, the c inFIG. 4 represents the change process of the voltage output from theoutput terminal of the PIN-type photodiode over time, and the d in FIG.4 represents the change process of the voltage output from the outputterminal of the capacitor C over time. As can be seen from FIG. 4, theoutput voltage of the PIN-type photodiode can be reduced from the set 0Vto about −2V by adjusting the timing of the signal, that is, thenegative voltage signal output by the PIN photodiode is furtheramplified to a smaller (a greater absolute value) voltage.

For example, the pixel structure may further include an X-ray conversionlayer. As shown in FIG. 2A, a PIN-type photodiode structure with a X-rayconversion layer is shown. The X-ray conversion layer is provided on thephotodiode. The X-ray conversion layer is used to convert X-rays intooptical signals, that is, this pixel structure can be applied to anX-ray flat panel detection device.

It is to be noted that the X-ray conversion layer may be directlyprovided on the photodiode or indirectly provided on the photodiode.

As shown in FIG. 2A, the PIN-type photodiode structure with the X-rayconversion layer includes a substrate 10, such as a glass substrate, agate electrode 1 formed on the substrate 10, a gate insulating layer 13formed on the gate electrode 1, an active layer 2 formed on the gateinsulating layer 13 corresponding to the position of the gate electrode,a source-drain layer 3 formed on the active layer 2, a first passivationlayer 4 formed on the source-drain layer 3, a second source-drain layer5 formed on the first passivation layer 4, a PIN junction 6 formed onthe second source-drain layer 5, the PIN junction 6 formed on the secondsource-drain layer 5, an ITO cover layer 8 formed on the PIN junction 6,and an intermediate insulation layer 7, such as a resin layer 7. Inaddition, the structure may further include a second passivation layer 9formed on the intermediate insulation layer 7. A shielding layer, suchas a metal shielding layer, may also be formed on the second passivationlayer 9. In addition, for example, a protective layer 20, such as aresin protective layer, for protecting the panel, as well as a nitridebarrier layer, an ITO pad layer, etc. may also be formed. For example,in addition, an X-ray protective layer 11 is formed on the protectivelayer 20. For example, the X-ray conversion layer can be formed by usingGdOS (gadolinium oxysulfide) or CsI (cesium iodide) material. The X-rayconversion layer is configured to convert X-rays to visible light. Forexample, the X-ray conversion layer is formed by a coating process or adeposition process, but the embodiments of the present disclosure arenot limited thereto. For another example, a via hole may also be formedin the intermediate insulation layer and the second passivation layer 9,and a bias metal line 19 is connected to the ITO cover layer 8 throughthe via hole.

The active layer in the figures refers to an I layer in the PIN, i.e.,an intrinsic layer grown in the PN junction, which performsphotoelectric conversion effect on the light obtained by X-rayconversion.

FIG. 2B illustrates a MSM metal semiconductor photoelectric conversiondevice. For example, the MSM metal semiconductor photoelectricconversion device may include a substrate 10, such as a glass substrate;a gate electrode 21 and a first ground layer 23 formed on the substrate10, for example, the gate electrode 21 and the first ground layer 23 maybe formed of the same metal material in the same process; a gateinsulating layer 24 formed on the gate electrode 21 and the first groundlayer 23; a first active layer formed on the gate insulating layer 24corresponding to the gate electrode 21, for example, the first activelayer is a-Si; a source-drain layer 25 formed on the first active layer;a first intermediate insulation layer 27 formed on the source-drainlayer 25, the first insulation layer may be formed of, for example, aresin material; a first via hole 28 formed in the first intermediateinsulation layer 27; a second ground layer 33 formed on the firstintermediate insulation layer 27, for example, the second ground layer33 may be formed of the same material as the first ground layer 23; asecond intermediate insulation layer 37 formed on the second groundlayer 33 and the first intermediate insulation layer 27; a second viahole 38 formed in the second intermediate insulation layer 37, thesecond via hole 38 is communicated with the first via hole 28; and anelectrode 29 formed on the second intermediate insulation layer 37. Forexample, a high voltage signal can be applied to the electrode 29 andapplied to the source and drain electrodes through the via hole. Inaddition, another active layer, such as an a-Si layer, may be formed onthe second intermediate insulation layer 37 and the electrode.

In addition, the pixel structure may also include a signal readoutcircuit, as shown in FIG. 5. For example, for an AD71124, the signalreadout circuit performs signal integration and amplification, signaldouble sampling and ADC conversion through an integrated circuit IC. Thesignal readout circuit is connected to the signal amplification circuitin FIG. 1 through Anx. For example, as a peripheral hardware, the signalreadout circuit can be accessed from Data in FIG. 1A. The signal readoutcircuit is connected to the data signal line. The signal reading circuitcan read the voltage signal on the data signal line and transmit thevoltage signal to the terminal, and the terminal can convert the voltagesignal into an image signal for viewing.

An embodiment of the present disclosure also provides a flat paneldetection device. The flat panel detection device may include the pixelstructure of the flat panel detection device described in any one of theforegoing examples.

An embodiment of the present disclosure also provides a camera system,which includes the above-mentioned flat panel detection device. Thecamera system may be a CCD camera system or a CMOS camera system. Thiscamera system can be applied to medical examinations. The flat paneldetection device can transmit the detected voltage signals to acorresponding terminal (e.g., a computer), which can convert theelectrical signals into image signals and display the correspondingimages for viewing.

The pixel structure of the flat panel detection device, the flat paneldetection device and the camera system provided by the presentdisclosure include a photodiode, a first switching transistor, and asignal amplification circuit connected to the photodiode and the firstswitching transistor. The photodiode works under the action of a reversevoltage, and the photodiode can convert the collected optical signalsinto electrical signals, that is, when exposed to light, the photodiodewill produce hole electron pairs. Under the action of an external biasfield, the electron and hole pairs move in opposite directions to form acurrent, and this current forms stored charges in the storage capacitorof the photodiode. When the scan signal causes the first switchingtransistor to be turned on, the photodiode can output a given voltagesignal to the signal amplification circuit, and this voltage signal canbe output to the data line after being amplified by the signalamplification circuit. In other words, in this process, the signalamplification circuit is provided between the photodiode and the firstswitching transistor to increase the actual signal output to the dataline, that is, the detection signal of the flat panel detection deviceis increased, which is beneficial to improve the signal-to-noise ratioof the flat panel detection device, so that the detection effect of theflat panel detection device is improved and then the quality of theobtained images is improved.

The above are only exemplary embodiments of the present disclosure, andthe scope of the present disclosure is not limited thereto. Any changesor substitutions that can be readily thought of by one of ordinary skillin the art within the technical scope disclosed in the embodiments ofthe present disclosure shall fall in the scope of the presentdisclosure.

1. A pixel structure of a flat panel detection device, comprising: aphotodiode configured to collect optical signals and convert the opticalsignals into electrical signals, the photodiode comprises a positiveterminal and a negative terminal, and the negative terminal is connectedto a bias voltage signal terminal; a signal amplification circuit, asignal input terminal of the signal amplification circuit is connectedto the negative terminal of the photodiode, and a signal output terminalof the signal amplification circuit is connected to a first node; and afirst switching transistor, a control electrode of the first switchingtransistor is connected to a scanning signal line, a first terminal ofthe first switching transistor is connected to a data signal line, and asecond terminal of the first switching transistor is connected to thefirst node.
 2. The pixel structure according to claim 1, wherein thesignal amplification circuit comprises: a second switching transistor, acontrol electrode of the second switching transistor is connected to afirst voltage signal terminal, a first terminal of the second switchingtransistor is connected to a second voltage signal terminal, a secondterminal of the second switching transistor is connected to a secondnode, and the second node and the first node are connected together tobecome one node; a third switching transistor, a control electrode ofthe third switching transistor is connected to the second node, and afirst terminal of the third switching transistor is the signal inputterminal of the signal amplification circuit; and a bootstrap circuit,one terminal of the bootstrap circuit is connected to the secondterminal of the third switching transistor, and the other terminal ofthe bootstrap circuit is the signal output terminal of the signalamplification circuit.
 3. The pixel structure according to claim 2,wherein the bootstrap circuit is a capacitor.
 4. The pixel structureaccording to claim 1, wherein the photodiode is ametal-semiconductor-metal type photodiode structure.
 5. The pixelstructure according to claim 2, wherein the third switching transistoris an n-type thin film transistor.
 6. The pixel structure according toclaim 1, wherein the photodiode is a PIN-type photodiode structure. 7.The pixel structure according to claim 2, wherein the third switchingtransistor is a p-type thin film transistor.
 8. The pixel structureaccording to claim 1, further comprising an X-ray conversion layerdisposed on the photodiode, and the X-ray conversion layer is configuredto convert a X-ray into an optical signal.
 9. The pixel structureaccording to claim 1, further comprising a signal readout circuit, andthe signal readout circuit is connected to the data signal line.
 10. Thepixel structure according to claim 8, wherein the X-ray conversion layeris made of gadolinium oxysulfide or cesium iodide material.
 11. Thepixel structure according to claim 4, wherein themetal-semiconductor-metal type photodiode structure comprises: asubstrate; a gate electrode and a first ground layer formed on thesubstrate; a gate insulating layer formed on the gate electrode and thefirst ground layer; a first active layer formed on the gate insulatinglayer corresponding to the gate electrode; a source-drain layer formedon the first active layer; a first intermediate insulation layer formedon the source-drain layer; a first via hole formed in the firstintermediate insulation layer; a second ground layer formed on the firstintermediate insulation layer; a second intermediate insulation layerformed on the second ground layer and the first intermediate insulationlayer; a second via hole formed in the second intermediate insulationlayer, and the second via hole is communicated with the first via hole;an electrode formed on the second intermediate insulation layer; and asecond active layer formed on the second intermediate insulation layerand the electrode.
 12. The pixel structure according to claim 6, whereinthe PIN-type photodiode structure comprises: a substrate; a gateelectrode formed on the substrate; a gate insulating layer formed on thegate electrode; an active layer formed on the gate insulating layercorresponding to a position of the gate electrode; a source-drain layerformed on the active layer; a first passivation layer formed on thesource-drain layer; a second source-drain layer formed on the firstpassivation layer; a PIN junction formed on the second source-drainlayer; an ITO cover layer formed on the PIN junction; an intermediateinsulation layer formed on the ITO cover layer; a second passivationlayer formed on the intermediate insulation layer; a shielding layerformed on the second passivation layer; and a protective layer formed onthe shielding layer; wherein the X-ray conversion layer is formed on theprotective layer.
 13. A flat panel detection device, comprising thepixel structure of the flat panel detection device according to claim 1.14. A camera system, comprising the flat panel detection deviceaccording to claim
 13. 15. The pixel structure according to claim 3,wherein the photodiode is a metal-semiconductor-metal type photodiodestructure.
 16. The pixel structure according to claim 15, wherein thethird switching transistor is an n-type thin film transistor.
 17. Thepixel structure according to claim 16, wherein the photodiode is aPIN-type photodiode structure.
 18. The pixel structure according toclaim 17, wherein the PIN-type photodiode structure comprises: asubstrate; a gate electrode formed on the substrate; a gate insulatinglayer formed on the gate electrode; an active layer formed on the gateinsulating layer corresponding to a position of the gate electrode; asource-drain layer formed on the active layer; a first passivation layerformed on the source-drain layer; a second source-drain layer formed onthe first passivation layer; a PIN junction formed on the secondsource-drain layer; an ITO cover layer formed on the PIN junction; anintermediate insulation layer formed on the ITO cover layer; a secondpassivation layer formed on the intermediate insulation layer; ashielding layer formed on the second passivation layer; and a protectivelayer formed on the shielding layer; wherein the X-ray conversion layeris formed on the protective layer.
 19. The pixel structure according toclaim 17, wherein the third switching transistor is a p-type thin filmtransistor.
 20. The pixel structure according to claim 19, furthercomprising an X-ray conversion layer disposed on the photodiode, and theX-ray conversion layer is configured to convert a X-ray into an opticalsignal.